How Hot Does Water In Espresso Machines Get?

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Ever wondered what the water temperature in your espresso machine is? Most espresso machines don’t have a temperature gauge so what can you expect? Here’s what you want to know.

The boiler in espresso machines is usually kept just under the boiling point. The optimal brew temperature for espresso is 90 to 96 degrees Celsius. The water cools down a little from the boiler to the coffee grounds. Modern digital controllers are much better at keeping a stable temperature.

Espresso machines are all different and can be a bit complicated. Below we’ll go into the differences and what you should look for.

How hot do espresso machines get?

How hot does an espresso machine get? What are we talking about exactly? No the whole machine is heated. The thing that’s heated in an espresso machine is the water. The water is heated in the boiler. This is basically an electric kettle which is closed off so it becomes pressurized. That boiler is filled with hot water and steam once it’s up to temperature?

So how hot is that water in the boiler after warming up? Usually, the boiler is kept just under the boiling point. The optimal temperature to brew espresso is 90-96 degrees Celsius but the maximum temperature in an espresso machines boiler is usually a bit higher because the water loses some heat on the way to the coffee.

A popular enthusiast home espresso maker is the Gaggia Classic. This is a fairly standard example of a good espresso machine. This machine keeps the temperature at a maximum of 98.5 degrees Celsius.

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The exact temperature depends on the specific machine. On most espresso machines, the boiler temperature is not adjustable by the user. There are a few models where this is possible but they’re usually the more expensive models.

Also, the water doesn’t stay at the same temperature the whole time. Temperature controls differ in accuracy and some types can have up to 10 degree swings in temperature while others keep the boiler temperature within one degree. How is that possible? It depends on the control mechanism, more on that below.

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Also, on machines that are plumbed in to a water line and automatically refill the boiler, pulling water out of the boiler also pulls it in at the same time which drops the temperature.

Pressurestat or PID?

The temperature swings and how big they are, are mostly the result of the way the temperature is controlled. Ideally you would want the temperature to be always the same so you know what you’re going to get.

There are two ways espresso machines control the boiler temperature: Pressurestat and PID. We can get into how they work exactly but let’s keep it simple:

A pressurestat is a mechanical device that measures the pressure in the boiler. When the pressure becomes too high (according to the pre-set pressure in the pressurestat), the heating element is turned off. And when the pressure becomes too low, the heating element is turned on. The problem with this type of control is that it reacts to temperature changes with a delay so it overshoots the ideal temperature a little and lets it cool down a bit too much on the other end. That means the temperature swings over time are quite large.

A PID is a digital temperature controller. It measure the temperature more accurately and can react to temperature changes much faster. Good PID controllers also predict the temperature changes before they happen and can preempt a temperature drop by turning on the heating element at exactly the right time. This has as a result that the temperature is held within 1 degree of the set temperature.

Another benefit of a PID is that many machines that have one allow you to actually control the temperature yourself while that’s not possible with a pressurestat.

If you’re buying a new espresso machine, definitely look for one with a PID because it’s just going to be more consistent and potentially brew better espresso. It’s usually listed pretty clearly in the specifications of an espresso machine so it’s not difficult to find out.

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Brew temperature vs. boiler temperature

The water temperature in the boiler and the water that comes out of the machine are not exactly the same. The water comes out of the group head which is basically a big metal block. Cold metal cools down water very quickly. And for espresso you only need a little bit of water so it will be cooled down quite a bit.

Espresso is usually brewed with water 90-96 degrees Celsius. That is the temperature of the water that hits the coffee puck. Since that is very close to the temperature in most boilers, you’ll want to make sure everything is preheated. You can simply do this by running some hot water through the group head with the basket in place without any coffee grounds. This way the hot water brings the metal up to temperature.

On high end super automatic machines this isn’t possible to do yourself because you don’t have any actual control over the flow of water. However, those machines often have other ways of preheating the metal parts.

Does the temperature of the water really matter all that much? It’s actually more important than you might think. The temperature of the water that hits the coffee grounds impacts how much you extract from those grounds. In general, the hotter the water, the quicker all the compounds dissolve so the higher the extraction. Too much or too little extraction are both bad for the taste so a good barista can use temperature to influence this.

How easy it is to extract the coffee grounds depends on the variety of beans, origin location, roast and grind size. However, to make the most of the beans you have, it either takes a lot of experimenting or you’ll have to have a lot of knowledge.

Most domestic espresso machines don’t have a temperature control. That means you’ll have to use the water temperature you get. However, you can play around with how much you pre heat the group head. If the water is too hot (espresso is too bitter), you can pre heat the lines and group head less so the excess heat is absorbed. On the other hand, if the coffee is a bit too sour, you can try preheating the metal parts more.

Kitchen temperature

While modern espresso machine boilers tend to be better insulated than older models, heat still escapes. The heat escapes by heating up the exterior and the air around the boiler. The hot exterior and hot air warm up the rest of the space the espresso machine is located in.

That will heat up your kitchen over time especially if the kitchen is smaller and it’s a hot day. For many people this is a reason to turn off their espresso machine even if turning it off might actually use more energy in the end.

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